1. Field of the Invention
The present invention relates to supplementary lighting devices utilizing an electroluminescent lighting element and a control system. In particular, the present invention relates to an electronic and mechanical control system coupled to an electroluminescent lighting element in order to provide user-adjustable light intensity, automatic output compensation, and an automatic daytime shutoff feature.
2. Related Art
Supplementary lighting devices, such as night lights, are well known and commonly used for security and safety purposes. For example, supplementary lighting devices can be used to illuminate passageways and stairways to assist night travel or escape in an emergency. They are also commonly used to relieve night anxiety in children, decrease the probability of burglary, and may provide accent lighting.
Several different types of lighting elements can be used in supplementary lighting devices. For example, incandescent bulbs, fluorescent bulbs, neon-type gas discharge elements, and electroluminescent (EL) elements are possible lighting elements for supplementary lighting devices. When choosing a lighting element for a supplementary lighting device, several factors such as cost, safety, longevity, and illumination are generally taken into consideration.
Incandescent lighting elements offer low initial cost and are easily replaceable. Incandescent lighting elements also offer relatively bright light, which is preferable in security type applications. This bright light, however, is not desirable in night light type applications. Further, incandescent lights burn at very high temperatures. In a supplementary lighting type application, the bulbs are generally small such that the glass enclosure is close to the element. These supplementary lighting devices are generally located near the ground, within easy reach of small children. Therefore, incandescent lights create a safety risk to children. The point source emission of an incandescent light is less preferable than wide area emissions.
Neon type lighting elements could also be used in supplementary lighting devices. Neon lights are low cost. However, they are generally not user-replaceable, therefore the entire device must be discarded when the lighting element fails. Neon light elements, however, can last several years, although they initially have a precipitous rate of decline of output. Hence, the light they emit for most of their life is only a small fraction of their initial output. Neon lights are also generally dim. Neon lights are cool, thereby presenting less of a safety hazard than incandescent lights.
Fluorescent lighting elements are also used in supplementary lighting devices. Fluorescent lighting elements have a high initial cost, but can generally be replaced. However, because fluorescent lighting elements are generally difficult to find, supplementary lighting devices using them are generally throw-away type units. Fluorescent lighting elements produce a wide range of colors, and are generally very bright, without being a point source emission. Fluorescent lights are also generally cool, reducing the safety risk associated with hot lighting elements. Fluorescent lighting elements have a relatively long life span, but toward the end of their useful life, they often experience flickering of the lighting element.
Recently, electroluminescent (EL) lighting elements have become increasingly popular for use in supplementary lighting devices. EL lighting elements provide wide-area emission, are cool (i.e., will not burn to the touch), and have a very long life. Most EL lighting elements used in supplementary lighting devices are connected directly across the 110 volt, AC power from a common household outlet. However, these EL lighting elements have the disadvantage that they are generally dim, are not replaceable, and their intensity fades gradually over their life span. Additionally, EL lighting elements utilized in supplementary lighting devices also generally remain activated even during the day, when their relatively dim light is not required.
There exist well-known techniques for increasing the light intensity of EL lighting elements above that which is generated by connecting them across 110 AC power lines. Methods for increasing the output of EL lighting elements include altering the voltage, altering the oscillation frequency of the alternating electricity, varying the duty cycle, and/or varying the waveform. However, these methods for increasing the output EL lighting elements still suffer from some of the same drawbacks as conventional EL lighting elements. For example, power boosted EL lighting elements still suffer illumination declines over the life of the light. Further, the amount of light cannot be controlled for specific applications.
Supplementary lighting devices, regardless of the lighting element utilized, can also present a safety hazard to children due to their connection to a wall socket. These supplementary lighting devices are generally inserted into wall sockets located near the floor, within easy reach of small children. Children tend to play with the rear of the lighting device, where it is connected to the wall socket. Children can potentially burn themselves if they touch the blades of the supplementary lighting device while it is still connected to the wall socket.
As can be seen from the description above, there exists a need for a supplementary lighting device which includes the advantages of EL lighting elements while accounting for the disadvantages of such systems.
The present invention addresses these disadvantages by providing a supplementary lighting device with a user-adjustable dimmer that works in conjunction with a control system to vary the intensity of an EL lighting element.
The dimmer, preferably mechanically or optically, adjusts the amount of light detected by a light sensor from the EL lighting element. Therefore, by adjusting the dimmer, the amount of light actually detected by the light sensor is artificially varied, and the information from the light sensor is inputted into the control system, which then adjusts the amount of power provided to the EL lighting element in a closed loop feedback system. This arrangement simultaneously allows the control system to adjust for ageing of the EL lighting element.
Furthermore, the light sensor, or an additional one, may simultaneously detect ambient light, and depending on the amount of ambient light detected, the control system can completely shut off the EL lighting element. This provides a xe2x80x9cdaytime offxe2x80x9d feature which conserves the EL lighting element and improves longevity of the device.
The EL lighting element is also replaceable. The device is designed such that a guide-way aligns the EL lighting element into mechanical and electrical contact with the control system. The guide-way is the only path from the user-accessible area of the device to the control system electronics. In addition, the device may be designed such that the EL lighting element is not accessible until the device is disconnected from a power source. In particular, the window covering the EL lighting element is coupled to the housing of the supplementary lighting device via a fastener which cannot be uncoupled without first disconnecting the device from the power source. This allows for safe replacement of the EL lighting element.
Another feature of the present invention is a safety device to prevent electrocution on electrical connection blades of the device while the device is still connected to a power source. In particular, a protector covers the electrical connection blades when the blades are removed from a power source. The protector retracts as the connection blades are inserted into a power source, and extends to cover the connection blades as the connection blades are removed from the power source.